Asymmetric synthesis of highly enantioenriched 2-substituted piperidines and 6-substituted piperidine-2-ones by a combination enantioselective hydrazone allylation with ring closing metathesis

An efficient method for the asymmetric synthesis of highly optically pure 2-substituted piperidines and 6-substituted piperidine-2-ones from aldehydes was developed by a sequence of enantioselective hydrazone allylation and ring closing metathesis. This method was found to be effective for a variety of substrates, showing substrate generality. The methodʹs synthetic utility was illustrated in concise synthesis of the alkaloid (R)-(−)-coniine.